But as early as Sunday, BP will begin ramping up a system that could begin collecting nearly double that amount – even with the containment cap off.

This system is separate from the new “sealing cap” that engineers are now trying to fit atop the failed blowout preventer. As a result, even if BP runs into trouble as it attempts to put on the more robust sealing cap – as past experience suggest is possible – the company could still be collecting nearly 35,000 barrels (1.47 million gallons) of oil a day in the meantime.

It means that the removal of the cap might not significantly worsen oil-collection efforts – even in the short term.

In fact, this separate system could collect a majority of all the spewing oil even without the cap, according to one estimate. Retired Coast Guard Adm. Thad Allen, who is overseeing the response effort, on June 18 said he thought the flow rate from the well was in the neighborhood of 35,000 barrels a day.

The ultimate solution – shutting off the flow of oil entirely by drilling a relief well – is currently slated for completion some time in August.

Introducing ... the Helix Producer

The new system set to come on line Sunday works independent of any cap because it involves a valve on the side of the blowout preventer called the “kill line.” A ship called the Helix Producer, which can process about 25,000 barrels a day, will connect to the kill line. BP is already using the kill line’s twin, the “choke line,” to siphon about 9,000 barrels of oil a day to a ship called the Q4000.

Even with the cap off, the Q4000 is collecting an average of 8,000 barrels of oil daily, said Kent Wells, BP’s senior vice president of exploration and production, on Saturday.

So when the Helix is operating at full capacity – which could take a few days – it and the Q4000 could bring collection capacity to nearly 35,000 barrels a day irrespective of the cap. With the old cap on, BP had been capturing roughly 26,000 barrels a day and interruptions of a day or more were common. A lightning strike and an accident with a robot both resulted in the collection of significantly less oil for a time.

Scientists have suggested that between 35,000 and 60,000 barrels of oil could be gushing from the wellhead daily.

Building a better cap

The ramping up of the Helix comes as BP is also trying to bolt a new and better fitting cap to the top of the blowout preventer.

The old cap, which was removed Saturday, was fitted atop the sawed-off stump of the riser pipe. Using remotely controlled robots, engineers will try to unbolt from the blowout preventer that stump of the riser pipe and in its place affix the new cap assembly, which weighs 100 tons and is 30 feet tall.

[Editor's note: The original misstated the height of the new assembly.]

BP officials were hopeful that the cap could be in place as soon as Monday. If it works, the cap – along with the Helix and Q4000 – is expected to collect virtually all the oil leaking from the well, though trickles could still escape if the seal is not perfect.

With all these efforts set to succeed or fail in the next few days, this week is shaping up to be one of the most important since the Deepwater Horizon exploded and sank in late April. That’s partly because hurricane Alex is forcing BP’s hand.

Hurricane Alex's impact

BP and the Coast Guard had wanted to space out these operations, bringing the Helix on line a week ago and then assessing the situation. It is possible that the Helix, Q4000, and old cap might have collected all the oil, making the new cap unnecessary.

But high waves from hurricane Alex delayed the deployment of the Helix and also showed how vulnerable to hurricanes the current collection system is. Even though the hurricane never approached the spill site, BP almost had to abandon its oil collection.

The pipes attached to the old cap were ill suited to weather storms. The new cap will include two flexible riser pipes, which will make it easier for ships to connect to them before and after a hurricane passes. Moreover, the new cap will have more oil-collection capacity.

With a week or more of clear weather forecast, BP and the Coast Guard are scrambling to try to get as many parts of new system as possible ready before another storm hits.